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NomachineApplication

CVE-2021-33436

HIGH · 7.3 CVSS v3.1 Published 2022-04-28
Fix available
A fix is available. Upgrade to 6.15.1 / 7.5.2 or later.
See remediation →
73/100
Remediation priority · Elevated

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
NoMachine for Windows prior to version 6.15.1 and 7.5.2 suffer from local privilege escalation due to the lack of safe DLL loading. This vulnerability allows local non-privileged users to perform DLL Hijacking via any writable directory listed under the system path and ultimately execute code as NT AUTHORITY\SYSTEM.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

NoMachine for Windows versions prior to 6.15.1 and 7.5.2 contain an unsafe DLL loading vulnerability where the application loads dynamic link libraries from directories in the system PATH without proper validation. Local attackers can place malicious DLLs in writable PATH directories, which get loaded by NoMachine components running with elevated privileges, enabling execution as NT AUTHORITY\SYSTEM.

MitigationUpgrade NoMachine for Windows to version 6.15.1 or 7.5.2 or later to obtain the safe DLL loading fix. As a temporary mitigation, audit PATH directories for write access and remove unnecessary write permissions.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
NomachineApplication
Affected:>= 6.0.0, < 6.15.1>= 7.0, < 7.5.2

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Confirm NoMachine installation
    Check for NoMachine installation by looking for the application in Program Files (C:\Program Files\Nomachine or C:\Program Files (x86)\Nomachine) or by checking the Windows Registry at HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\NoMachine or HKEY_LOCAL_MACHINE\SOFTWARE\Nomachine
    Affected if NoMachine is not installed on the system
  2. Determine installed NoMachine version
    Open Add or Remove Programs in Windows Control Panel, locate NoMachine, and note the version number displayed, or check the version in the NoMachine program files directory
    Affected if The installed version is 6.0.0 or higher but below 6.15.1, or 7.0 or higher but below 7.5.2
  3. Verify if NoMachine services run with elevated privileges
    Open Windows Services (services.msc), locate NoMachine service(s) such as nxd or nxservice, right-click and select Properties, then check the 'Log on as' account. Also verify by running 'sc qc nxservice' or 'sc query nxservice' from command prompt
    Affected if The NoMachine service logs on as LocalSystem (NT AUTHORITY\SYSTEM) or another elevated account, enabling privilege escalation if a malicious DLL is loaded
  4. Identify writable PATH directories
    Open Command Prompt and run 'echo %PATH%' to list all directories in the system PATH. For each directory, check write permissions by right-clicking the folder in File Explorer, going to Properties > Security, and reviewing the write permissions for Users or authenticated users
    Affected if Any directory in the system PATH is writable by a local non-privileged user, allowing placement of malicious DLLs that NoMachine will load

You are affected if NoMachine is installed with a version between 6.0.0 and 6.15.1 (exclusive), or between 7.0 and 7.5.2 (exclusive), and runs with elevated privileges while the system PATH contains directories writable by local attackers.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 6.15.1 / 7.5.2 or later
Fixed in 6.15.17.5.2
Interim mitigation

Upgrade NoMachine for Windows to version 6.15.1 or 7.5.2 or later to obtain the safe DLL loading fix. As a temporary mitigation, audit PATH directories for write access and remove unnecessary write permissions.

Recommended fix High confidence

NoMachine 6.15.1 (for 6.x branch) or NoMachine 7.5.2 (for 7.x branch)

  1. Identify the currently installed NoMachine version on the Windows system
  2. If version is 6.0.0 through 6.15.0, plan upgrade to version 6.15.1 or later
  3. If version is 7.0.0 through 7.5.1, plan upgrade to version 7.5.2 or later
  4. Download the appropriate NoMachine installer for the target fixed version from the official NoMachine website (knowledgebase.nomachine.com)
  5. Run the NoMachine installer with administrative privileges
  6. Follow the on-screen installation prompts to complete the upgrade
  7. Restart the NoMachine service if prompted
  8. Verify the installed version matches the expected fixed release

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Nomachine Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,040
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,664.

Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-33436 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data